[lldb] Add OS plugin property for reporting all threads

Currently, an LLDB target option controls whether plugins report all
threads. However, it seems natural for this knowledge could come from
the plugin itself. To support this, this commits adds a virtual method
to the plugin base class, making the Python OS query the target option
to preserve existing behavior.

Author: felipepiovezan

lldb/include/lldb/Target/OperatingSystem.h

@@ -61,6 +61,8 @@ class OperatingSystem : public PluginInterface {
 
   virtual bool IsOperatingSystemPluginThread(const lldb::ThreadSP &thread_sp);
 
+  virtual bool DoesPluginReportAllThreads() = 0;
+
 protected:
   // Member variables.
   Process

lldb/source/Plugins/OperatingSystem/Python/OperatingSystemPython.cpp

@@ -386,4 +386,8 @@ lldb::ThreadSP OperatingSystemPython::CreateThread(lldb::tid_t tid,
   return ThreadSP();
 }
 
+bool OperatingSystemPython::DoesPluginReportAllThreads() {
+  return m_process->GetOSPluginReportsAllThreads();
+}
+
 #endif // #if LLDB_ENABLE_PYTHON

lldb/source/Plugins/OperatingSystem/Python/OperatingSystemPython.h

@@ -60,6 +60,8 @@ class OperatingSystemPython : public lldb_private::OperatingSystem {
   // Method for lazy creation of threads on demand
   lldb::ThreadSP CreateThread(lldb::tid_t tid, lldb::addr_t context) override;
 
+  bool DoesPluginReportAllThreads() override;
+
 protected:
   bool IsValid() const {
     return m_script_object_sp && m_script_object_sp->IsValid();

lldb/source/Target/Process.cpp

@@ -1182,7 +1182,7 @@ void Process::UpdateThreadListIfNeeded() {
           // See if the OS plugin reports all threads.  If it does, then
           // it is safe to clear unseen thread's plans here.  Otherwise we
           // should preserve them in case they show up again:
-          clear_unused_threads = GetOSPluginReportsAllThreads();
+          clear_unused_threads = os->DoesPluginReportAllThreads();
 
           // Turn off dynamic types to ensure we don't run any expressions.
           // Objective-C can run an expression to determine if a SBValue is a

lldb/source/Target/TargetProperties.td

@@ -223,7 +223,7 @@ let Definition = "process_experimental" in {
   def OSPluginReportsAllThreads: Property<"os-plugin-reports-all-threads", "Boolean">,
     Global,
     DefaultTrue,
-    Desc<"Set to False if your OS Plugins doesn't report all threads on each stop.">;
+    Desc<"Set to False if your Python OS Plugin doesn't report all threads on each stop.">;
 }
 
 let Definition = "process" in {